1 // Copyright Louis Dionne 2013-2017 2 // Distributed under the Boost Software License, Version 1.0. 3 // (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) 4 5 #include <boost/hana/assert.hpp> 6 #include <boost/hana/config.hpp> 7 #include <boost/hana/equal.hpp> 8 #include <boost/hana/optional.hpp> 9 namespace hana = boost::hana; 10 11 main()12int main() { 13 BOOST_HANA_CONSTEXPR_LAMBDA auto incr = [](auto x) -> decltype(x + 1) { 14 return x + 1; 15 }; 16 17 BOOST_HANA_CONSTEXPR_CHECK(hana::sfinae(incr)(1) == hana::just(2)); 18 19 struct invalid { }; 20 BOOST_HANA_CONSTANT_CHECK(hana::sfinae(incr)(invalid{}) == hana::nothing); 21 } 22